The present invention pertains generally to devices and methods for guiding catheters through the vasculature of a patient. More particularly, the present invention pertains to devices and methods for positioning a catheter tip at a predetermined site in the vasculature of a patient. The present invention is particularly, but not exclusively, useful for positioning the tip of a cardiac cryoablation catheter at a predetermined site in the vasculature for surgical procedures requiring effective heat transfer.
Guidance and positioning mechanisms are important considerations in the manufacture and operation of an invasive catheter. Specifically, the ability to easily and accurately guide the catheter through a patient""s vasculature to a target site is an essential catheter characteristic. Once the catheter is near the target site, the ability to then accurately position the catheter tip at the target site is also important.
Several devices have been previously suggested for the purpose of steering a catheter through the vasculature of a patient For example, U.S. Pat. No. 1,060,665, which issued to Bell on May 6,1913 for an invention entitled xe2x80x9cCatheterxe2x80x9d, incorporates a pre-bent stiffening member located at the catheter""s distal end for use of the member""s bending bias in steering the catheter through the vasculature. Recently, more complex devices have relied on a pull-wire to deflect the catheter tip. In general, these mechanisms have included concentric or eccentric pull-wires that generate an eccentrically applied force on the tip of the catheter. For example, U.S. Pat. No. 4,456,017, which issued to Miles for an invention entitled xe2x80x9cCoil Spring Guide with Deflectable Tip,xe2x80x9d incorporates a concentric core wire for this purpose. In contrast, U.S. Pat. No. 4,586,923, which issued to Gould et al., uses an eccentric wire for the same purpose. Furthermore, devices have also been proposed which will bias the deflection of a catheter tip in a predetermined plane. An example of such a device is disclosed in U.S. Pat. No. 4,886,067, which issued to Palermo for an invention entitled xe2x80x9csteerable Guidewire with a Soft Adjustable Tip.xe2x80x9d In the Palermo patent, such a bias is established by flattening the core wire. Another device that is often used for steering a catheter through the vasculature of a patient involves a guidewire that is pre-positioned in the vasculature across a target site. The catheter is then engaged with the guidewire, and is advanced over the guidewire through the vasculature to the target site.
At the target site, some surgical applications require that the tip of the catheter be accurately positioned. In particular, for cryoablation procedures, the tip of a cryoablation catheter must be accurately positioned to contact tissue at the target site for cryoablating the tissue. Importantly, a cryoablation catheter has unique structural aspects and thermodynamic properties that must be considered in the design of its guidance and positioning mechanism. Specifically, a cryoablation catheter is typically designed with a closed tip portion that forms an expansion chamber. In operation, a cryogenic fluid is introduced into the expansion chamber through a supply line to rapidly cool the tip portion. Consequently, tissue in contact with the tip portion at the target site is cryoablated. Importantly, whatever guidance mechanism may be used to position the tip portion in the vasculature, it must not interfere with the intended operation of the cryoablation catheter.
Prior art mechanisms for guiding and positioning a catheter generally have not been designed to accommodate the particular structural aspects required for the catheter""s intended application. Accordingly, they have not specifically considered the requirements for operation of a cryoablation catheter. For instance, existing over-the-wire guiding mechanisms that pass a guidewire through the catheter tip cannot be used with a cryoablation catheter because the required closed tip portion of a cryoablation catheter prevents the guidewire from fully extending through the catheter. In any event, the guidewire must not compromise the expansion chamber or interfere with the flow of cryogenic fluid to and from the expansion chamber.
In light of the above, it is an object of the present invention to provide a device and method for advancing a catheter through a patient""s vasculature and for positioning the catheter tip at a predetermined site in the patient. Another object of the present invention is to provide a device and method for guiding a cryoablation catheter through a patient""s vasculature without compromising the expansion chamber in the catheter tip. Still another object of the present invention is to provide a device and method for guiding and positioning a catheter in the vasculature of a patient that is relatively easy to manufacture, is simple to use, and is comparatively cost effective.
The present invention is directed to a system and method for guiding a cryocatheter through the vasculature of a patient to position the distal end of the cryocatheter at a predetermined site in the vasculature. As intended for the present invention, the system includes a connector that is incorporated with the distal end of the cryocatheter and is formed with a passageway configured to receive a guidewire. The guidewire is pre-positioned in the vasculature of the patient and leads to the predetermined site. When the connector is engaged with the guidewire, the cryocatheter can be advanced along the guidewire and through the vasculature to position the distal end of the cryocatheter at the predetermined site.
In detail, the cryocatheter includes a catheter and a tip. The catheter has a proximal end and a distal end, and is formed with a wall surrounding a lumen that extends between the proximal and distal ends of the catheter. The tip has a closed distal end and an open proximal end, and is formed with a wall surrounding a chamber. Structurally, the open proximal end of the tip is attached to the distal end of the catheter so that the chamber formed by the tip is in fluid communication with the lumen of the catheter. Preferably, the tip is substantially cylindrical-shaped and defines a longitudinal axis.
The system of the present invention further includes a tubular-shaped supply line that has a proximal end and a distal end. The supply line is positioned in the lumen of the catheter with its distal end located in the chamber. With this structure, in addition to the supply line, a fluid return lumen is established inside the catheter between the supply line and the inner wall of the catheter. Furthermore, the proximal end of the supply line is connected to a fluid supply, which is in fluid communication with the chamber through the supply line.
As indicated above, the present invention envisions a connector that is operationally associated with the tip of the catheter. In one embodiment of the present invention, this connector is an eyelet. For this embodiment, the eyelet has an annular shaped member that is formed with a passageway for receiving the guidewire. Additionally, the eyelet has an extension arm with one end attached to the annular shaped member. In one variation of this embodiment, the other end of the extension arm is fixedly attached directly to the tip.
In a variation of the xe2x80x9ceyeletxe2x80x9d embodiment for the present invention, the system also includes a post that extends axially from the closed end of the tip in a distal direction. For this embodiment, a ring is formed at the end of the extension arm opposite the annular shaped member and is configured to surround the post. Additionally, a cap is attached to the distal end of the post to hold the ring on the post, to thereby allow the annular shaped member of the connector to rotate (swivel) around the longitudinal axis.
In still another embodiment of the present invention, the connector is formed into the wall of the tip. Structurally, for this embodiment of the present invention, the connector is a passageway that is formed between the inner and outer surfaces of the tip wall. More specifically, the passageway extends between a first opening and a second opening, which are located on the outer surface of the tip wall. In yet another embodiment of the present invention, the connector is formed into the wall of the catheter. For this embodiment, the connector is a passageway that is formed between the inner and outer surfaces of the catheter wall. The passageway extends between a first opening and a second opening, which are located on the outer surface of the catheter wall. Importantly, in either case, the passageway should not compromise the expansion chamber or reduce the efficacy of the thermodynamic structure of the tip.